SAN DIEGO (CNN)As he sought to wrest the California Democratic Party's endorsement away from longtime Sen. Dianne Feinstein, her upstart challenger, Kevin de León, made an impassioned argument to state delegates Saturday that the time had come for a new generation of leadership in the Senate.

While he was not able to earn their endorsement outright, he did secure enough votes (54%) to prevent one for Feinstein, who received just 37 percent of the delegates' votes.

In an aggressive speech at the California Democratic Party convention, De León said Democrats deserve a progressive senator who fights on the "front lines," who doesn't "equivocate on the sidelines."

"I'm running for US Senate because the days of Democrats biding our time, biding our talk, are over," said De León, who is the leader of the California Senate. "Leadership comes from human audacity, not from congressional seniority."

He faulted Feinstein for her initial approach to President Donald Trump -- which infuriated Democratic activists here -- mocking her for saying last August that she believed Trump "can be a good president" if he had the ability to "learn and to change."

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Charging that Feinstein is out of step with the progressive direction of the party, De León pointed to a litany of issues where he said he disagrees with the senior senator, including school vouchers, allowing federal agents to spy on American citizens, and her past support of the wars in Iraq and Afghanistan.

He said he would never have supported prosecuting 13-year-olds as adults "in a criminal justice system propped up by institutional racism" (an apparent reference to her support for the 1994 crime bill). De León also chided Feinstein's approach to immigration, charging that he would never use the so-called Dreamers "as a bargaining chip."

"We demand passion, not patience. We speak truth to power," said De León said. "And we've never been fooled into thinking that Donald Trump could be a good president. ... Being good sometimes is not good enough."

Feinstein did not mention her Democratic opponent at all.

In the wake of the mass shooting in Parkland, Florida, she focused her remarks on her decades-long advocacy for an assault weapons ban, which was phased out in 2004. She criticized Trump for suggesting that teachers should be armed.

"I thought after Sandy Hook there would never be another school shooting, yet after Sandy Hook, 400 people have been shot in over 200 school shootings," Feinstein said. "Last year, 26 of us in the Senate introduced a new assault weapons ban, and passing it now is my quest. It's my mission. I am absolutely committed to achieving this."

"Now is the time to take those weapons of war off our streets," she said to applause.

De León got a far warmer welcome than his opponent on the convention floor. But he had to receive 60 percent of the delegate votes to get the Democratic endorsement, a threshold he did not meet.

De León enjoys a close kinship with many of the state delegates, who tend to be far more liberal than the average California voter.

Even had De León notched the endorsement, Feinstein is still heavily favored to win in November -- in part because of her nearly unlimited resources, and her support among California independents and some Republicans.

Dan Newman, a Democratic strategist for Lt. Gov. Gavin Newsom and US Sen. Kamala Harris, said a party endorsement for De León would be "the apex of his campaign," but that it was unlikely to have an impact on the outcome in the Senate race because of Feinstein's near universal name recognition.

"He still faces an electorate that largely doesn't know who he is, and the tremendous amount of respect and reverence for Senator Feinstein because of her decades of work, particularly on the issue that is energizing Democrats more than any other right now," said Newman, who supports Feinstein.

Governor's race

Delegates began voting Saturday evening on endorsements for the statewide races, including the US Senate seat and the California governor's race. The endorsement battle was far more competitive in California governor's race where John Chiang and Gavin Newsom were locked in a close race for the party's nod.

"The time for timidity is over," said Newsom, touching on his history of becoming the first mayor to marry same-sex couples, passing the state's highest minimum wage, and pushing for the first citywide universal health care plan when he was mayor of San Francisco. "My opponents in this race have spent a lot of time telling us what can't be done."

"My whole life we have faced down skeptics, defeatist Democrats who have suggested we need to pick our battles," Newsom said. "California has never succeeded by playing it safe."

Former Los Angeles Mayor Antonio Villaraigosa, made the case that his life experience growing up in poverty had prepared him for the challenges of the governor's office.

"Millions of Californians are worker harder than ever before, and they are still falling further and further behind," Villaraigosa said. "There are two Californias, one rich and getting richer, and another where millions of hardworking families are still struggling to make their California dream come true. But it doesn't have to be this way. They call us the Golden State and we can shine again."

Villaraigosa, who has long trailed Newsom with his fundraising efforts, threw a few jabs in his rival's direction. At one point, he noted that he learned about poverty and the middle-class struggle through his own life experience, not at "a panel at Davos."

Without mentioning their names, Chiang took shots at both Newsom and Villaraigosa. He alluded to the fact that both weathered embarrassing episodes when their past marital problems spilled into the public eye.

"You deserve a governor with integrity to lead and the character to make every Californian proud," said Chiang, who is state treasurer. "You deserve a governor you can trust, a governor with the credibility to go after sexual harassers."

Chiang tried to position himself as the best candidate to stand up to Trump, noting he had experience standing up to "racist bullies" when he was a child.

After the votes were tallied, no consensus was reached for a gubernatorial candidate. Newsom received the highest percentage of votes with 39%, followed by Chiang with 30%, Delaine Eastin with 20%, and Villaraigosa with 9%.

The endorsement caucuses Saturday night could also could be a key factor in narrowing the field in the seven congressional races in California that are key to Democrat's hopes of winning back the House of Representatives.

Party officials are concerned that the large field of Democratic candidates in several races -- including the contests to replace retiring Republican House members Darrell Issa and Ed Royce -- could actually put Democrats in a scenario where they split the vote, creating a path for the Republican candidates.

Though voting took place in those congressional races Saturday night, the results will not be final until they are certified on the convention floor Sunday.